Microstructural characterization and microhardness of rapidly solidified Al-Ce alloys

The microstructures of rapidly solidified Al-8 Cc and Al-20 Ce (wt.%) alloys have been characterized. The phases present in as-spun alloys are identified to be alpha-Al and alpha-Al11Ce3, identical to those in the ingot-like alloys. The microstructure of as-spun Al-8 Ce alloy is fully composed of irregular and elongated alpha-Al cells with intercellular alpha-Al11Ce3. In as-spun Al-20 Ce alloy, however, some zones comprise columnar and irregular alpha-Al dendrites with interdendritic alpha-Al11Ce3 and other zones comprise irregular alpha-Al microdendrites with interdendritic alpha-Al11Ce3. Age hardening effect is not observed in the present alloys. The microhardness changes little with time when annealing below 300 degreesC but sharply decreases when annealing at 400 or 500 degreesC, indicating that the thermal stability of as-spun Al-8 Ce and Al-20 Ce alloys rapidly deteriorates above 300 degreesC.